Fox News chairman and CEO Roger Ailes is demanding that Donald Trump apologize for comments he made about Megyn Kelly on Monday night following an airing of The Kelly File.

“Donald Trump’s surprise and unprovoked attack on Megyn Kelly during her show last night is as unacceptable as it is disturbing,” said Ailes in a statement released to EW. “Megyn Kelly represents the very best of American journalism and all of us at Fox News Channel reject the crude and irresponsible attempts to suggest otherwise.

The statement continues:

I could not be more proud of Megyn for her professionalism and class in the face of all of Mr. Trump’s verbal assaults. Her questioning of Mr. Trump at the debate was tough but fair, and I fully support her as she continues to ask the probing and challenging questions that all presidential candidates may find difficult to answer. Donald Trump rarely apologizes, although in this case, he should. We have never been deterred by politicians or anyone else attacking us for doing our job, much less allowed ourselves to be bullied by anyone and we’re certainly not going to start now. All of our journalists will continue to report in the fair and balanced way that has made Fox News Channel the number one news network in the industry.

Trump’s comments came via his Twitter account on Kelly’s first day back at The Kelly File following a brief vacation. “@megynkelly must have had a terrible vacation, she is really off her game. Was afraid to confront Dr. Cornel West. No clue on immigration!” Trump tweeted Monday.

“I liked The Kelly File much better without @megynkelly. Perhaps she could take another eleven day unscheduled vacation!”

.@megynkelly must have had a terrible vacation, she is really off her game. Was afraid to confront Dr. Cornel West. No clue on immigration!

Trump went on to retweet some of his supporters, many of whom commented on Kelly’s looks (one user went so far as to call Kelly a “bimbo”).

The presidential candidate’s war against Kelly began during a GOP primary debate from earlier this month, when she asked Trump about his tendency to call women “fat pigs, dogs, slobs, and disgusting animals” on his Twitter account. (“Only Rosie O’Donnell,” Trump replied.)

Following the debate, Trump said in an interview with CNN’s Don Lemon that Kelly had “blood coming out of her eyes – blood coming out of her wherever.” Trump was criticized for the sexist undertones of his remarks, but later insisted that “only a sick person” would think it was made in reference to Kelly’s period.

For Kelly’s part, she has personally chosen not to respond to Trump’s various personal attacks – which included speculation that she took a recent 10-day vacation because of Trump’s comments (a claim Fox News denied).

“Mr. Trump is an interesting man who has captured the attention of the electorate. That’s why he’s leading in the polls,” she said in an episode of The Kelly File on Aug. 10. “Trump, who is the frontrunner, will not apologize. And I certainly will not apologize for doing good journalism, so I’ll continue doing my job without fear or favor. And Mr. Trump, I expect, will continue with what has been a successful campaign thus far. This is a tough business and it’s time now to move forward.”